31 weeks pregnant
At 31 weeks you are in the third trimester, and your baby measures about 41 cm from head to heel and weighs about 1.50 kg, roughly the length of an A3 sheet, long side. Antenatal classes usually run around now, and the 31-week visit in a first pregnancy checks blood pressure, urine and the baby's growth.
Weighs about 1.50 kg, like a 1.5 L bottle of water. Averages from standard growth tables; your scan gives your baby's own numbers.
Your baby at 31 weeks
Rapid weight gain; all five senses are working. Curled in the fetal position and filling out with fat; the eyes open from about week 26.
How you might feel
Sleep is often broken by heartburn, a full bladder and the baby's movements, and forgetfulness and feeling clumsy are common.
Antenatal classes usually run around now.
Call the maternity unit today for any change in your baby's movements, bleeding, fluid loss, a severe headache or vision changes. 13 HEALTH (13 43 25 84) in Queensland; 000 in an emergency.
What's due this week in Australia
Whooping cough (pertussis) vaccine
Free under the National Immunisation Program in every pregnancy.
Lodge the Parental Leave Pay and Family Tax Benefit claims
You can lodge up to 3 months before the due date through myGov → Centrelink.
RSV vaccine (Abrysvo)
Free under the National Immunisation Program, one dose per pregnancy from 28 weeks and ideally before 36 weeks.
31-week antenatal visit (first pregnancy)
Blood pressure, fundal height, movements and a check of results.
Wills, guardianship, super and insurance
Make or update wills and name a guardian.
Coming up: 34-week antenatal visit
Blood pressure, fundal height, the baby’s position, birth preferences and pain relief, and a feeding plan.
Coming up: Pack the hospital bag and fit the car seat
A rear-facing restraint must be fitted before you can take the baby home.
Checklist for the week
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Questions about 31 weeks
How many months is 31 weeks pregnant?
About seven months.
What trimester is 31 weeks?
Week 31 is in the third trimester. In the Australian guidelines Hello Bub follows, the first trimester runs to 13 weeks, the second from 14 to 27 and the third from 28 weeks.
What do antenatal classes cover?
Signs of labour, pain relief, what happens in the birth suite, caesarean birth, feeding and the first days at home, usually with a tour of the maternity unit.
Written by the Hello Bub team; medical schedule follows the Australian Pregnancy Care Guidelines; last reviewed 3 November 2026.